The ethanol production from lignocellulosic agricultural waste which contains
cellulose and hemicellulose as the main component were another interesting alternative of
raw materials beside starchy or sugar materials. However, the presence of lignin in
lignocelluloses acts as the barrier to obstruct the enzyme accessibility to cellulose and
hemicelluloses. Pretreatment process is necessary to remove lignin and alter cellulose
structure to improve enzymatic hydrolysis. Each pretreatment has a different effect on the
cellulose, hemicellulose and lignin fraction. Thus, different pretreatment methods and
conditions should be chosen according to the process configuration selected for the
subsequent hydrolysis and fermentation steps. This paper reviews the most interesting
technologies for ethanol production from lignocellulose and it points out several key
properties that should be targeted for low-cost and advanced pretreatment processes.